Because Steve started with very high mileage on his first day it is inevitable that his cumulative average will regress downwards towards the mean, so that in itself is not necessarily worrying. But his rolling 4-day average has been below target in the last 8 days which means, as you say, he will have to step up a little in the coming days. He does remain above target (by 33 miles), but he has been steadily eating into the advantage he built up in the first week.